from struct import pack

class TribeDecodeError(Exception):
    def __init__(self, value):
        self.value = value
    def __str__(self):
        return repr(self.value)

# Seeks a 'tribe fw bit array for the next packet start.
# Takes an iterator
def packetseek(it):
    numbits = 0;
    while(it.next()):
        numbits += 1;         # Loop through all the junk bits

    # print "%d bits skipped." % (numbits)

# Fetch next byte from bitarray.
# Returns an int.
def fetchbyte(it):
    tempstr="";
    for x in range(0,8):
        #print it.next()
        tempstr = str(it.next())+tempstr;

    return int(tempstr, 2)

# fetch a number of bytes to extract a full packet
# The second optional argument is to ignore the post-signature check, needed for the initial greeting packet
def fetchpacket(it, ignorepostsig=False, packetindex=0):
    tempbyte=0;tempstr = "";temparray=[];

    tempbyte=fetchbyte(it);

    # Confirm pre-signature
    if(tempbyte != 0xA9):
        raise TribeDecodeError("Invalid packet pre-signature! Should be 0xA9. Found: " + hex(tempbyte));

    # Confirm post-signature
    for x in range(0,256):
        tempbyte = fetchbyte(it);
        tempstr+=pack("B", tempbyte);
        temparray.append(tempbyte);

    if not ignorepostsig:
        # Confirm post-signature
        for x in range(0,3):
            tempbyte = fetchbyte(it);
            if(tempbyte != 0x55 and packetindex != 0x80):
                raise TribeDecodeError("Invalid packet post-signature! Should be 3*0x55. Found: " + hex(tempbyte));

        # Print the mysterious checksum byte
        tempbyte = fetchbyte(it);
        print "Packet %s has checksum (?) %s" % (hex(packetindex), hex(tempbyte));

        # Sanity check
        tempbyte = fetchbyte(it);
        if(tempbyte != 0xff):
            raise TribeDecodeError("Sanity check. Packet should be followed by 0xff but isn't. Found: " + hex(tempbyte));


    return tempstr;

# main function
def tribefwdecode(infile, outfile, invert):
    f = open(infile, "r");

    bitarray = f.readlines();  # Fetch the array of bits

    # Validate the bit array and convert it to bool
    for i,b in enumerate(bitarray):
        b = b.strip();
        if (b != "0" and b != "1"):
            raise TribeDecodeError("Only 0 and 1 in the bit file, please! Found: " + b);
        else:
            if invert:
                bitarray[i] = 1-int(b);
            else:
                bitarray[i] = int(b);

    bititer = iter(bitarray);

    # Seek for the greeting packet.
    packetseek(bititer);
    fetchpacket(bititer, True)

    f = open(outfile, "w")

    packetidx = 0;

    while True:
        try:
            packetseek(bititer);        # Try to get a packet
        except StopIteration:
            break;                      # Detect end of file.

        # Parse packet and write it fo the file.
        packet = fetchpacket(bititer,False,packetidx)
        f.write(packet)

        packetidx += 1;

    # If we're done, close the file.
    f.close();
    print "File %s successfully parsed and written to %s" % (infile, outfile)


tribefwdecode("bits", "firmware2.bin", True)